Could you please update the Remmina packages? 1.0.0 is quite old, and Remmina 1.2 is now the current version upstream, with lots of bugfixes and feature upgrades. The existing packages have worked ok, but buggy (i.e. the NumLock bug), but it has worsened after the latest minor release (CentOS 7.2).

Works good. Remmina updated to the newer version, and gone is the num lock bug, together with the extra ones after updating to latest CentOS 7 release. After the update I wasn't able to access the top menu in an active session (activating grabbing of keyboard events, screen modes and so on). This is now possible again. Thanks. Perhaps make a notice of this, since Remmina after all works best of the available RDP clients on CentOS, and other distros. I understand Remmina could be found in the Fedora EPEL repository earlier, but that the application for some reason was removed.

Yes, that's correct. When having focus on another application, I must click on the application on the taskbar to work in the remote session. If not, the menu that pops up when clicking the right mouse button on the backgroud appears, or the Remmina window with the saved sessions. The entire GDM may become unresponsive when switching to the Remmina remote session with a left-click, not from choosing the remote session on the taskbar.

Does any of this happen if you connect to the remote host via xfreerdp from the command line?

No, haven't tried to connect with xfreerdp from the command line. But after trying some more, I found another parameter: clicking "grab all keyboard events" on the top menu of the RDP session. After last crash yesterday I restarted GDM, reconnected, but this time I didn't activate keyboard grabbing. And this time, GDM didn't become totally unresponsive, and the remote session lasted throughout the rest of the day. But if another window is active I have to click on the RDP session on the taskbar, otherwise I only get the right-mouse-button menu as if I right-clicked on the desktop background.

Installed without a glitch on CentOS 7.5 when doing 'yum update' with repo activated. Seems to work pretty good. Will try to activate keyboard grabbing, one thing that caused instability before. But, so far, so good.

I rebuilt the 1.2.0 SRPM from nux but although it built and started, any session I tried to connect to just sat there continually reconnecting and then erroring (repeat).

Downloaded remmina-1.2.31.3-1.fc29.src.rpm and ran that through mock, installed the resulting packages and all works... well, everything I tested so far. Had to edit the Fedora 29 spec file and comment out all the "Recommends:" lines as el7's rpmbuild does not understand those, otherwise no changes made.